Web printing machines



Oct. 1, 1968 HANS-RUDOLF MOSER ET AL. 3,403,622

WEB PRINTING MACHINES 2 Sheets-Sheet 1 Filed Sept. 14, 1966 Oct. 1, 1968HANS-RUDOLF MOSER ET AL WEB PRINTING MACHINES 2 Sheets-Sheet 2 FiledSept. 14, 1966 Fig. 3

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INVENTOR5 AQA/J- @001 F M55 g fi/Pwvs 2710525757 United States Patent3,403,622 WEB PRINTING MACHINES Hans Rudolf Moser, Utzensdorf, and HansThierstein, Kirchberg, Switzerland, assignors to Fritz Buser, A.G.,Wiler, near Utzensdorf, Switzerland, a Swiss body corporate Filed Sept.14, 1966, Ser. No. 579,349 Claims priority, application Switzerland,Sept. 16, 1965, 12,883/ 65 8 Claims. (Cl. 101-426) ABSTRACT OF THEDISCLOSURE A web printing machine of the kind having an endless conveyorbelt trained over two spaced-apart rollers, a printing table associatedwith the web-carrying upper conveyor flight, means for moving the upperflight intermittently to carry the web to and from the printing tableand means for continuously moving the lower flight, the latter meansincluding means for displacing the rollers in unison toward and awayfrom the respective ends of the printing table. Improved operation isachieved by (1) mounting the roller which is nearest the point ofengagement of the web with the conveyor belt for displacement in adirection inclined at an angle of -90 to the plane of the table and (2)engaging the web with the conveyor belt before the belt passes over thejust-mentioned roller.

Disclosure The present invention relates to web printing machines suchas screen printing machines.

In the case of screen printing machines, the textile or web which issupposed to receive the imprint is guided by means of a conveyor beltacross a printing table. This movement takes place intermittently sincethe screen printing has to be carried out during the time that the webis at a standstill. The periodic movement, in the case of several screenprinting machines of this kind, is produced through advancing elements,which for example have been arranged frictionally to engage the conveyorbelt on both sides of the printing table, in order to move it by oneunit length. For the drive of the advancing elements there may beprovided a piston which can slide within a cylinder and which can beacted upon by pressure oil, said piston being in constant connectionwith the advancing elements.

In the past, the periodic movement of the web that is to be printed hasbrought about the fact that during the intermittent movement not onlythe whole conveyor belt but also all elements in contact with it, suchas for example the rollers about which it is passed as well as therollers of a device for applying glue and of a washing arrangement, haveto be accelerated and decelerated. Therefore, a relatively large masshas had to be accelerated from the standing still position and then hasto be retarded to the standing still position, during which time theintermittent movement has to be carried out in the shortest possibletime or with the greatest possible speed in order to achieve goodeconomy in the operation of the machine. Because of all this, greatdriving forces have been needed for the intermittent operation. Beyondthat, the possibility has also existed that as a result of thisintermittent operation, deformations or sag in the conveyor belt mayresult which under certain circumstances would impair the precision ofthe printing. Another disadvantage of the prior intermittent operationis that the operative efliciency of rollers, which are in contact withthe conveyor belt and which are used for application of the glue and forthe washing process, changes depending on whether the conveyor belt isat a standstill or is in 3,403,622 Patented Oct. 1, 1968 motion. In manycases, too heavy an application of glue to the conveyor belt takes placewhen the belt is at a standstill, a fact which has an unfavorable effectwith regard to the evenness of the print later on when the web securedto the belt by that glue is being printed on.

For eliminating the aforesaid disadvantages, in our British Patent No.1,037,407, the rotatable elements or rollers carrying the conveyor beltare continuously moved in unison towards and away from the respectiveends of the conveyor belt. At the point where the web joins the conveyora supply roller, which may be heated, is provided for pressing the webonto the conveyor.

As the rotatable elements are displaced, the supply roller is alsodisplaced, so that during all the stages of operation, the web and theconveyor run off the supply roller and off the rotatable element, eventhough at a speed varying between a maximum and minimum value. Since thesupply roller, acting at the same time as deflecting roller for the webto be printed is displaceable, the latter cannot be arranged very closeto the web roll, which would result in an advantageous, continuouslyshorter web draw-01f. The acceleration and retardation occurring withthe variable conveyor speed and web speed, in addition to the long webfeed is particularly disadvantageous in the case of stretchable printingfabrics.

It is now the purpose of the present invention to provide a web printingmachine in which the aforesaid disadvantages are obviated.

According to the invention there is provided a web printing machinecomprising an endless conveyor trained around two rotatable elements,the upper flight of the conveyor being adapted to carry a web to beprinted to and from a printing table, means being provided operative onthe said upper conveyor flight for advancing the flight intermittentlywith intervening stops of given duration for printing onto the web,means for continuously moving the lower conveyor flight, which isbetween said rotatable elements, nothwithstanding intermittent movementof said upper conveyor flight, said rotatable elements being mounted formovement in unison towards and away from the respective ends of theprinting table, the rotatable elements being advanceable through apredetermined distance, one towards and one away from the printingtable, as the upper conveyor flight advances, and means responsive tothe stopping of the upper conveyor flight for retracting said rotatableelements for said predetermined distance while said upper conveyorflight is stationary, at least the rotatable element situated nearer thepoint where the web joins the conveyor, being displaceable above theplane of the printing table in a direction ingllined at an angle of atleast 45 to the plane of the ta 6.

In order that the invention may more readily be understood, thefollowing description is given, merely by way of example, referencebeing made to the accompanying drawings, in which:

FIGURE 1 shows schematically, in side elevation, one embodiment ofscreen printing machine according to the invention;

FIGURE 2 is an enlarged detail view of the machine according to FIGURE 1showing the means for driving the lower flight;

FIGURE 3 shows a speed diagram for the infinitely variable gear fordriving the lower flight;

FIGURES 4 to 6 show different positions of control wheels for speedregulation.

Referring to the drawings, in FIGURE 1 there is shown the printing table1 of a screen printing machine. A printing conveyor belt 2, which passesaround two opposite end rotatable elements in the form of rollers 3 and4, extends with its upper flight 2a over the surface of the table 1, sothat it is supported by the latter during printing. The lower conveyorflight 2b extends under the table 1 through a washing installation 5 anda glue application device 6. For driving the conveyor belt 2 in itsupper flight 2a in the direction of an arrow A there is provided apiston 8 slidable in a cylinder 7 and having driving elements providedon rods 9, which elements, during the advancing movement of the piston 8establish a releasable frictional connection with the belt 2. Theelements 10 may be, for example, hydraulically or magnetically operatedtongs or suction shoes. Displacement of piston 8 in cylinder 7 isproduced by the alternating action of pressurized oil on its two sides.This pressurized oil is pumped continuously by a pump 12 from a tank 11and is fed to the cylinder 7 by way of a reversing valve 13 throughpipes 14 and 15. The reversing valve 13 is controlled, for example, by atime-controlled servoelement 16.

The two rollers 3, 4 are displaceable from the end positions shown insolid lines to the end positions 3, 4' shown in chain lines. This meansthat the roller 4 mounted at the entry of the machine can be raised andlowered, and the roller 3 is horizontally displaceable. In order to keepthe conveyor belt 2 tensioned, despite the displaceability of therollers 3, 4, the bearings 17, 18 of the rollers 3, 4 are connectedtogether by a pull member, for example a chain 19, which is passedaround deflecting wheels or sprockets 20-22. Instead, however, eachbearing 17, 18 may be engaged by its own, for example weight-loaded,pull member, tending to pull the deflecting rollers 3, 4 apart fortensioning the conveyor belt 2.

The displaceable rollers 3, 4 with the conveyor belt 2 and the chain 19,when the machine is stationary, constitute a stable, motionlessarrangement. The natural weight of the roller 4 pulls the roller 3 bymeans of the chain 19 for tensioning the endless conveyor belt 2 to theright. in the drawing. The conveyor belt 2 is also deflected by thestationary rollers 23, 24.

The web draw-off, for example fabric draw-off, is effected from a reel25. The web 27, after travelling a short distance from the reel 25, runsover heating and pressing roller 26 onto the lower flight 2b of theconveyor belt 2. When the web 27 and conveyor belt 2 run together, theyare both connected together temporarily by sticking for fixing the webin the usually several successive stages of the printing operation withdifferent printing stencils, relative to the latter. The heating andpressing roller 26 is mounted on a lever 29, pivotal on the pin 28, andcan bear with varying pressure on the roller 24. The particularapplication pressure between the rollers 24, 26 depends on the speed ofthe lower flight 2b and hence on the peripheral speed of the roller 24.The roller 24 drives a hydraulic pump 30, the hydraulic fluid from whichacts through a conduit in a cylinder '32 and presses the heating andpressing roller 26 against the roller 24 by means of a piston 33 and thelever 29, with a pressure dependent on the speed of roller 24 and thusensures constant adhesive force.

The lower flight 2b of the conveyor belt 2 is driven by a roller 34,which in its turn is driven by an electric motor 36 by means of a chain35 via an infinitely variable gear, not shown. The ends of a chain 37are secured by cross-pieces 38 to the chain 19. The chain. 37 drives awheel '39. Thence the drive is effected via a control device, to beexplained later, by means of a chain 40 onto the infinitely variablegear, not shown, of the motor 36. The particular position of thecross-pieces 38, relative to the stationary motor 36, corresponds to adefinite, adjusted driving speed of the roller 34. The displacementtravel of the chain 19, and hence of the cross-pieces 38 serves as anadjustment parameter for the controllable drive of the lower flight 2b.The control is shown in FIGURE 2 and following figures and is explainedlater.

Instead of being fed straight from the reel to roll 26 as illustrated at27, the fabric may be fed, as illustrated at 41, from the reel 25 over astraightening apparatus (not shown), a fabric web guide and possiblyother devices, and thence via a deflecting roller 42 to the heating andpressing roller 26. In this method of guiding the fabric, the advantageof a short fabric entry between the reel 25 and the roller 26 does notexist.

The operation of the machine with the driving arrangement described forthe continuous movement of the lower flight 2b takes place, inprinciple, in such a manner that during the standstill times of theupper flight 2a, a certain length of belt is always conveyed from theexit side of the upper flight 2a to the entry side thereof by thedisplacement of the rollers 3 and 4 from the chain line position 3, 4'approximately to the solid line position. On the other hand, due to themovement of the rollers 3 and 4 during each intermittent movement of theupper flight 2a, part of the belt length required by the lower flight 2bwill be compensated, since during this movement, the roller 3 isdisplaced in the same direction, i.e., in the direction of the arrow A,and the roller 4 will be displaced vertically downward. Thus, the speedof the lower flight 2b can be kept much lower during the repeat movementof the upper flight 2a than the speed of the upper flight 20 wouldrequire per se.

This arrangement has the advantage that no part of the conveyor beltcomes to a stop at the washing installation 5, at the glue applicationdevice 6 and at the sticking point on the rollers 24, 26 as long .as themachine is in operation. Due to the fact that the lower flight 2b runsoff the rollers 24, 26 continuously, a continuous draw-ofl of the fabricfrom the reel 25 is ensured, either with the fabric 27 or 41. Due to thestationary rollers 24, 26, the draw-01f speed of the fabric 27 or 41 isequal to the speed of the lower flight 2b, and like the latter, issubstantially less than the speed of the upper flight 2a during theintermittent movement. During the operation of the machine and at thecommencement of the intermittent movement of the upper flight 2a, therollers 3, 4 are approximately in the solid line position shown. Theelements 10 engage the top flight and displace the latter by a repeatlength in the direction of the arrow A. The roller 34 drives the lowerflight 2b at a lower speed than the element 10 drives the upper flight2a. Since, therefore, the belt length is not conveyed from the lowerflight 2b over the roller 4 to the upper flight 2a, and at the roller 3a larger belt length of the upper flight 2a obtains than can be conveyedby the slower drive of roller 34, the roller 4 moves vertically downwardand the roller 3 outwardly to the right until the rollers 3, 4 aresituated approximately in their position according to 3', 4'. During theprinting process the upper flight 2a is at rest. The roller 34,continuing to drive, exerts a pull on the lower flight 2b at the roller3, so that the latter moves from its position 3' to the leftapproximately into the solid line position. Owing to the positivecoupling of the rollers 3, 4 by means of the chain 19, the roller 4 ismoved upwardly from its position 4' into approximately the solid lineposition, so that then a fresh working cycle can recommence. Thedisplacement path of roller 4 is above the plane of the table 1.

The maximum distance of rotation of the wheel 39 serving to control themotor 36 is determined by the displacement of the rollers 3, 4 to theirrespective two end positions. A rotated end position of the wheel 39 maybe used, in the manner explained later, for stopping the entire screenprinting machine. An end position of the rollers 3, 4 corresponding tothis position of the wheel 39 should naturally not occur during normaloperation.

By means of the control elements 37-40 for the infinitely variable gearof the motor 36, a speed of the lower flight 2b is adjusted inaccordance with the particular position of the chain 19 and hence inaccordance with the position of the deflecting rollers 3, 4. The speedvariation of the lower flight 2b may be designed such that a slightacceleration and a slight retardation occurs, and such that the maximumspeed of the continuously moved lower flight 2b is approximately halfthe speed of the intermittently moved upper flight. In respect of time,the speeds of the upper and lower flights 2b and 2a may overlap, suchthat during the drive of the upper flight 2a, the lower flight 2b isaccelerated to maximum speed; during the stoppage of the upper flight2a, the drive of the lower flight is retarded to minimum speed, andthen, on the next working cycle again, it accelerates slowly togetherwith the rapidly accelerated movement of the upper flight 2a.

Instead of the vertical direction of displacement of the roller 4, thelatter may also be adapted to be displaced at an angle of at least 45 tothe plane of table 1. The direction of displacement of the roller 4 maythus be an angle of 45 90" to the plane of table 1, the advantage of theshort fabric entry being retained. The roller 3 may also be arranged tobe displaced in a direction which is inclined to the plane of the table1 in the same way as the roller 4.

The control of motor 36 for driving the lower flight operates asfollows:

A wheel 43 is mounted freely rotatable on the spindle of wheel 39. Thewheel 39 carries two mutually opposite pins 44, 45, and the wheel 43 hasa stop 46 for these pins 44, 45 (FIG. 4). The position of the wheels 39,43 according to FIG. 4 occurs at the position of the crosspieces 38fixed to the chain 19 according to FIGS. 1 and 2. The rollers 3, 4 aresituated in the solid line position according to FIG. 1, which is theend position. The cross-pieces 38 in FIGS. 1, 2 have been displaced tothe extreme right, and the wheel 39 has rotated the wheel 43 by means ofpins 44, 45 in the anticlockwise direction to the position according toFIGURE 4. In this position of wheel 43, the infinitely variable gear ofmotor 36 has been set to zero speed by means of the chain 40. Theextreme right-hand cross-piece 38 in FIGURES l, 2 is in a position 47,assumed stationary. In the diagram according to FIG. 3, the displacementpath S of the rollers 3, 4, and hence of the cross-pieces 38 is plottedas abscissa; the ordinates show the particular driving speed n of thewheel driving the chain 35 (FIG. 1). In position 47 of the cross-piece38, the speed n is equal to zero, as already mentioned (FIGURES 2, 3).

If, now, the movement of the upper flight 2a is started, thecross-pieces 38 in FIGS. 1, 2 are displaced to the left. The wheel 39can be rotated by the chain 37 in the clockwise direction to the solidline position according to FIG. 5, Without the wheel 43 being rotated.In this position according to FIG. 5, the cross-pieces 38 have beendisplaced to the left by the distance to position 49, assumed stationary(FIGS. 2, 3), the speed n remaining zero (FIG. 3). On furtherdisplacement of the crosspieces 38 to the left and rotation of the wheel39 in the clockwise direction, the wheel 43 is rotated by the pin 44 inthe clockwise direction to the dash line position according to FIG. 5,and the speed increases linearly with increasing rotation of the wheel43 (FIG. 3). Before the end position 3' of the roller 3, correspondingto the position 48 of the displaceable cross-piece 38 in FIG- URE 2, thespeed n, has been reached after the distance s the movement of the upperflight 2a is terminated and the cross-piece 38 moves to the right againin FIGS. 1, 2. At the same time, the wheel 39 is rotated in theanticlockwise direction ont of the dash-line position of FIG- URE 5; thewheel 43 remains unchanged. The speed n thus remains constant (FIGURE3). Up to rotation of wheel 39 into the solid line position, accordingto FIG- URE 6, the wheel 43 remains stationary unaltered and n remainsadjusted. If at this point of time, the next movement of the upperflight 2a again starts, the speed in still remains adjusted. Ondisplacement of the rollers 3, 4 through their distance s minus s to andfro, the lower flight 2b will then be moved continuously at the samespeed. Owing to tolerances occurring after several repeat lengths, andowing to speed fluctuations, the reciprocating path of the rollers 3, 4may vary somewhat. This means that the wheel 39 no longer rotatesto-andfro without action on the wheel 43, but the pin 45 swings the stop46 to position 46' (FIGURE 6). A lower speed n is now selected (FIGURE3). The reciprocating path of the rollers 3, 4 is now s minus s (FIGURE3). On further operation of the screen-printing machine, the speed 21 isadjusted. The speed may therefore hunt between n and n during operation.Both speeds n n however, may lie very close to each other. A change fromn to n-,, and vice versa only occurs after a number of repeats of theupper flight 2a. Movement of the lower flight is thus efiected atapproximately constant speed.

While preferred embodiments of the present invention have beendescribed, further modifications may be made without departing from thescope of the invention. Therefore, it is to be understood that thedetails set forth or shown in the drawings are to be interpreted in anillustrative, and not in a limiting sense, except as they appear in theappended claims.

What we claim is:

1. A web printing machine comprising an endless conveyor trained aroundtwo rotatable elements'the upper flight of the conveyor being adapted tocarry a web to be printed to and from a printing table, means beingprovided operative on the said upper conveyor flight for advancing theflight intermittently with intervening stops of given duration forprinting onto the web, means for continuously moving the lower conveyorflight, which is between said rotatable elements, notwithstandingintermittent movement of said upper conveyor flight, said rotatableelements being mounted for movement in unison towards and away from therespective ends of the printing table, the rotatable elements beingadvanceable through a predetermined distance, one towards and one awayfrom the printing table, as the upper conveyor flight advances, andmeans responsive to the stopping of the upper conveyor flight forretracting said rotatable elements for said predetermined distance whilesaid upper conveyor flight is stationary, at least the rotatable elementsituated nearer the point where the web joins the conveyor, beingdisplaceable above the plane of the printing table in a directionsubstantially perpendicular to the plane of the table.

2. A web printing machine according to claim 1, wherein the lower flightof the conveyor is led round a deflecting roller at the point where theweb joins the conveyor, the web being pressed against this roller by asupply roller, around which the web is passed on its way from a supply.

3. A web printing machine according to claim 2, wherein the supplyroller is heated.

4. A web printing machine according to claim 1, wherein said tworotatable elements are connected together by means of a pull member,which is carried over deflecting wheels to keep the conveyor taut.

5. A web printing machine according to claim 1, wherein the lower flightis driven by a motor through an infinitely variable gear.

6. A web printing machine according to claim 4, wherein said pull memberis carried over a first deflecting wheel, coaxial with which there isprovided a control wheel acting on and infinitely variable gear, and thetwo wheels having stops whereby the control wheel may be driven in bothdirections of rotation, by the first wheel in the manner of a follow-uppointer.

7. A web printing machine according to claim 6, wherein the first wheelhas two diametrically opposite pins and the control wheel has a stopengageable by these pins for rotating the control wheel in bothdirections of rotation through approximately relative to the controlwheel.

8. In a web printing machine of the type including a supply of web to beprinted, a printing table, an endless conveyor having an upper flightand a lower flight, said conveyor being trained around first and secondrotatable 7 elements so as to provide an upper flight adapted to carry alength of the web to, and from said printing table and so as to providea lower flight, means operative on said upper flight for intermittentlyadvancing said upper flight with intervening stops to permit printing onthe web, means for continuously moving said lower flight, which isbetween said rotatable elements, notwithstanding intermittent movementof said upper flight, said rotatable elements being mounted for movementin unison toward and away from the respective ends of said printingtable and being advanceable through a predetermined distance, one towardand one away from said printing table, as said upper flight advances,and means responsive to the stopping of said upper flight for retractingsaid rotatable elements for said predetermined distance while said upperconveyor flight is stationary, the improvement which permits the initialpoint of contact between said endless conveyor and said web to belocated close to said supply of web to thereby reduce the length of webwhich is subjected to acceleration and retardation by intermittentoperation of said upper run, said improvement also effecting improveduniformity of the speed at which said web is withdrawn from said supply,said improvement comprising mounting means associated with the rotatableelement which is situated nearer the point Where said web engages saidconveyor for displacing said last-named rotatable element above theplane of said printing table in a direction inclined at an angle of atleast 45 to theplane of said table, said improvement further comprisingpress ing roller means in advance of said last-named rotatable element,with respect to the direction of conveyor movement, for pressing saidweb into contact with said conveyor, said pressing roller means beingfixed against movement corresponding to displacement of said last-namedrotatable element.

References Cited UNITED STATES PATENTS ROBERT E. PULFREY, PrimaryExaminer.

F. A. WINANS, Assistant Examiner.

